Eutrophication: mapping the first steps that lead to dead zones

Dead Zones - an alarming term used to describe aquatic areas where oxygen levels are so greatly reduced as to push out or kill most fish, plants, and shellfish. It's a dramatic descriptor for the extreme end result of two much more complex processes: eutrophication and hypoxia. While both of these can occur naturally, they are also increasing with greater frequency due to man-made causes.

Eutrophication is the introduction of natural or artificial substances, such as nitrates or phosphates, into an aquatic system. Sometimes this can be due to natural occurrences - such as runoff from rains that include a high percentage of decaying plant matter or animal waste. This has been known to occur in some lakes and rivers, particularly in areas of the world where seasonal changes can be extreme - long droughts followed by heavy rains.

However, eutrophication is often caused by the introduction of fertilizers and treated or untreated sewage. And when this happens there begins a series of cascading disturbances that can ultimately lead to a dead zone. Everything from increased nitrogen which upsets the proper balance of dissolved nitrogen and oxygen levels; the expanded growth of algae and phytoplankton which can reduce sunlight, upsetting the process of photosynthesis that produces oxygen and impacting bottom dwelling creatures; a feedback loop that is generated by more decaying plant material from the increase algal growth - all begin to enter into the picture at varying degrees.

When dissolved oxygen levels are reduced to the point at which a wide swath of animal and plant life is severely impacted, then you have a hypoxic or low-level oxygen condition. This can lead to a major shift in the aquatic ecology through either the migration or elimination of species or by predation from animals than can better withstand or even prefer low-oxygen environments. Another offshoot can be the development of toxic bacteria, which has been linked as a possible culprit in a recent die-off off hundreds of thousands of sardines in Redondo Beach, California. While not yet determined to be the definitive culprit, the overall water condition outside the harbor in Redondo Beach is being scrutinized as a polluted, low oxygen area that may have allowed for a large mass of sardines to be affected by neuro-toxin bacteria.

The World Resources Institute (WRI) has been compiling evidence of eutrophication and hypoxia on a global scale for some time. WRI provides an interactive map whereby one can view areas of either or both of these conditions. It also includes areas that have actually shown improvement, which means that this is a process that can be reversed.

While it is true, as mentioned earlier, that eutrophication and hypoxia can be a naturally-occurring process, by using the map's time frame feature - where you can select segments of time in years ranging back to 1850 - one can see the increase in these conditions over the years. Currently, the World Resources Institute lists 762 impacted coastal areas, 228 effected by eutrophication and 479 effected by hypoxia. Fifty-five areas show improvement. The institute is constantly searching for information on scientifically-verified sites so as to provide as accurate of a picture as possible.

Aquatic ecology has its ups and downs, its own ways of pummeling itself and then recovering - something it developed over hundreds of thousands of years. But today there is clear evidence that mankind is throwing unexpected blows from which the oceans, lakes, and rivers are unable to recover. Better control of our use of fertilizers and our disposal of sewage and other chemicals is the obvious solution, but it requires the political will, economic incentive, and public support to produce positive action.

View the interactive map at World Resources Institute.

Ocean Dead Zones: low oxygen areas are still growing

Ocean researchers and many conservationists have heard of oceanic low-oxygen or "dead zones" wherein large areas of ocean have lower-than-normal levels of oxygen. To a large extent, these areas are normal or somewhat predictable - deepwater and seasonal movements of water; all part of the ocean's normal process of oxygen intake, use, and replenishment.

But there are more and more signs from throughout the world that these dead zones are becoming more frequent and growing in size. From both coasts of Africa, to South America to the Pacific Northwest, dead zones are becoming a real problem, killing off some aquatic species, displacing others, and affecting the ocean's relationship with the atmosphere - a relationship that provides a majority of our breathable air.

A recent article in the online McClatchy newspaper outlines what has been happening in the Pacific Northwest, along the Oregon/Washington coastline. Some scientists believe it's too soon to tell whether the root cause - a warming of the surface waters that acts as a cap to suppress the normal cycle of deepwater to shallow, or upwellings and downwellings - is due to global warming, but it's high on their list of suspects.

Some might think that it's a sign of ocean acidification, but this is a different process taking place here, as well illustrated in the article. However, in any case, the net effect of the coast of Oregon and Washington is tangible, with piles of dead Dungeness crab and 25-year old sea stars littering a sea floor covered with a higher-than-normal bacteria layer.

"Areas of hypoxia, or low oxygen, have long existed in the deep ocean. These areas — in the Pacific, Atlantic and Indian oceans — appear to be spreading, however, covering more square miles, creeping toward the surface and in some places, such as the Pacific Northwest, encroaching on the continental shelf within sight of the coastline.

'The depletion of oxygen levels in all three oceans is striking,' said Gregory Johnson, an oceanographer with the National Oceanic and Atmospheric Administration in Seattle."

If these low-oxygen zones continue to increase in size and/or frequency, the ocean ecology will have to make adjustments, some that will be severe and that we will feel as they impact commercial fisheries. But scientists are not sure just how far-ranging these changes could be. After all, they have no reference models or examples to turn to - we are heading into unknown territory.

"Scientists are unsure how low oxygen levels will affect the ocean ecosystem. Bottom-dwelling species could be at the greatest risk because they move slowly and might not be able to escape the lower oxygen levels. Most fish can swim out of danger. Some species, however, such as chinook salmon, may have to start swimming at shallower depths than they're used to. Whether the low oxygen zones will change salmon migration routes is unclear.

Some species, such as jellyfish, will like the lower-oxygen water. Jumbo squid, usually found off Mexico and Central America, can survive as oxygen levels decrease and now are found as far north as Alaska."

Read entire McClatchy article.

Omega-3: beneficial fatty acid has an ecological downside

We have all heard of the benefits of seafood; in particular the omega-3 fatty acids that are found in oily fish like salmon, mackerel, and sardines. In fact, according to a recent article in TIME magazine, the market for omega-3 supplements has doubled since 2006, reaching $1 billion in sales.

One fish in particular, the menhaden, plays an important role in the production of omega-3. But its popularity has equated to overfishing and that has produced some definite negative consequences on water quality and other industrial fish populations.

Not a typical fish for the dinner table, the menhaden is a filter feeder and acquires its omega-3 potential by feeding on omega-3-rich algae. In addition to a general filtering of the water (up to 7 gallons per minute!), the menhaden helps to keep the level of algae in check. Algal blooms deplete oxygen, adding to the production of "dead zones" in the ocean. While the populations of menhaden being fished within its Atlantic and Gulf of Mexico range, have not necessarily reached a critical status, their reduced numbers have produced impacts that have been felt in other fisheries, like the Chesapeake Bay which wrestles with declining commercial fish populations due to dead zones.

But are there alternatives? One possible alternative being developed is the industrial production of the omega-3-rich algae on which menhaden feeds. Makes sense - just go to the source. As part of the emerging field of algae production (also an alternative to corn-based ethanol), it's been shown that omega-3 can be derived from algae in addition to flax seed and canola oils.

For fishermen who have been bringing in menhaden for years (it's also used for fishmeal for feeding poultry and farmed-raised salmon), a shift from commercial fishing boats to high-tech algae farms is not an easy or likely transition. This is part of the economic dilemma that we face when we consider what steps are necessary to protect species or the environment. As has been experienced in the automotive industry and other collapsed fisheries, important as these changes are, they are not without their major hurdles.
Click here to read the TIME magazine article by Tim Padgett.